Modern imagesetters and platesetters utilize optical scanners to write or record images for subsequent reproduction or to read a prerecorded image at a predefined resolution rate. Such scanners may write or record images on or read prerecorded images from various media including photo or thermal sensitive paper or polymer films, photo or thermal sensitive coatings or erasable imaging materials, an aluminum or other metal base printing plate, or other type media. The medium is typically mounted on an imaging surface which may be planar or curved and then scanned with an optical beam.
The primary components of modern imagesetting and platesetting systems include an image processor to generate and/or edit an image and a raster image processor (RIP) for converting data signals from the image processor into signals which can be understood by a controller which controls the imaging by the imagesetter or platesetter. The imagesetter or platesetter itself typically includes an imaging head such as a scan assembly which is often disposed and movable within a drum cylinder in which the recording or recorded medium is mounted. The controller, in accordance with the signals from the RIP and its own programmed instructions, generates signals to control the optical scanning so as to write images on or read images from the medium mounted within the drum cylinder by scanning one or more optical beams over the inside circumference of the drum cylinder while the cylinder itself remains fixed. A typical scan assembly of a cylindrical drum type image system may include a spin mirror or other optical device to direct the light beam over the inside circumference of the drum cylinder, as will be well understood by one skilled in the art.
In order to provide quality imaging, it is imperative that the medium to be imaged be properly positioned on the support surface of the imaging system. This is especially true in color imaging where color separations printed on separate sheets are subsequently superimposed on the printing press. Conventionally, registration pins, punches, visual targets or notches are utilized for this purpose. (See "Pin Registration: Making Sense Of the Formats and the Philosophy", The Seybold Report on Publishing Systems, pp. 12-18, Dec. 23, 1996.) In this regard, the applicable registration devices are fixedly mounted along the medium support surface in a predetermined configuration such that when the medium is loaded into the imaging system it is positioned against the registration pins, or punched or notched, i.e., perforated, while clamped or otherwise held in the imaging position. Although suitable for use in imaging systems which are intended to image only media of one width, or which will be used for imaging with only one punch or notch configuration, such fixed registration devices are less than ideal for use in imaging systems which are intended to image media of varying widths or which require a plurality of configurations to be used for a single image or media width.
Typically, it is assumed that the medium being loaded onto the support surface prior to imaging is properly positioned by forcing the medium to be imaged against the registration pins or by forcing the medium against the support surface and holding it in place. However, if the medium is being loaded in a skewed disposition, the medium may contact less than all the registration pins and therefore be skewed on the support surface at the time of imaging. By punching or notching the media while held in place against the support surface, this error can often be overcome.
In certain cases, it is necessary to notch or punch the medium subsequent to the imaging of a medium on an auxiliary machine. This provides greater flexibility in terms of the different configurations or widths which can be accommodated. The medium can then be mounted to the cylinders of the print processor using the notches or punches. In such cases, misregistration errors can occur during the punching or notching operation due to an accumulation of tolerances during each operation, since each operation for imaging, punching and printing requires registration for optimal image quality.
Punches and notches may take any desired shape, circles and slots, or portions thereof, being the most common shapes. Different configurations may also require different punch or notch sizes and/or placements. Additionally, certain configurations may require varying size or shape punches or notches and/or a combination of punches and notches. Conventional fixed configuration notches and punches make it difficult to accommodate such special requirements.
Another problem with a fixed punch configuration is that the leading left edge of the medium must be justified against a stop in order to properly align the punches with the image. Hence, the medium must be moved perpendicular to the load direction to properly align the punches with the image.